VEGA VEGASCAN 850 Modbus signal output - Manual (Page 14)

14 Modbus signal output VEGASCAN 850
Start
Slave
address
Function
code
Exception
Code
Error
Check
End
No. of
bytes
Value
range
Meaning
Structure of the answer VEGASCAN 850 to Modbus master
ASCII answer telegram on enquiry with function code 06
1 2 2 2 2 2
:
1 .. 247 0x84
1 .. 3 LRC CR LF
Exception code = 1
: 0 1 8 6 0 1 X X CR LF
Data transmission with Modbus ASCII
Error messages in ASCII mode
Errors in the telegram of function code 04 (Read Input Register) are commented by an error
message (Exception Response). The most significant bit of the function code is set to 1 (cor-
responds to function code + 80H). In the byte Exception Code, the error is named in coded
form (see error overview).
Error overview:
Exception Code Meaning
1 unpermitted function
2 unpermitted start register
3 unpermitted number of registers
Example for error message:
A DCS value should be collected from a VEGASCAN. The slave address of VEGASCAN is set
to 1.
In the enquiry telegram, an unpermitted function code (06) has been inadvertently enquired.
Therefore the following answer telegram is displayed: